This invention relates to a finish material for window openings.
In the building trade, it is conventional to build a wood frame wall using relatively rough lumber and finish the interior surface of the wall with gypsum wallboard (GWB). In the event that the wall has a window opening, a window frame is installed with the inner face of the window frame offset outward from the interior of the wall. The return surfaces, which surrounding the window opening and are perpendicular to the interior of the wall, may be finished using either of two principal methods which are known in the building trade as wood wrap and drywall or GWB wrap.
In accordance with the wood wrap technique, a wood sill is placed at the bottom of the window opening in the lower horizontal return portion and is attached to the framing lumber, typically by use of nails, and wood trim pieces are installed in the vertical return portion of the window opening and in the upper horizontal return portion and are attached to the framing lumber. A molding profile is installed over the vertical wall face, typically by nailing to the exposed edges of the trim pieces, in order to conceal the rough edge of the GWB around the opening.
The wood wrap technique is subject to disadvantage because wood is a high maintenance finish material. Nail holes must be filled after installation and a surface finish must be applied. Further, when the structure settles, a wood sill may separate from the GWB on the interior surface of the wall, leaving unsightly cracks.
In accordance with the drywall wrap technique, GWB is attached to the upper and lower horizontal return portions and to the vertical return portions and suitable reinforcing corner beading is installed to protect the corner transition between the vertical wall and the return surfaces bounding the window opening.
The drywall wrap technique is subject to disadvantage because GWB is not a tough material and therefore is not well suited to the type of stress that is applied to a bottom sill.
In construction of a frame wall, lumber that is nominally vertical might not in fact be vertical. Most of the time this is not a significant problem, because any error is not visible. However, if a stud at the edge of a window opening is used for alignment of finish material and it is out-of-plumb, the finish material may itself be out-of-plumb, which could be objectionable.
It is possible to gauge the maximum departure of the sides of a window opening from vertical using a carpenter's level. The error is typically less than 1/4" over the height of the window opening.
When a wood wrap is installed, it is usual to use shims to adjust the spacing between the vertical trim pieces and the studs at the vertical sides of the window opening so that the trim pieces are vertical. A similar technique is not used in the drywall wrap technique and consequently there is a significant possibility that the nominally vertical sides of the window opening are not in fact vertical.
It is generally considered that the wood wrap trim technique provides a more attractive finish than the drywall wrap technique. On the other hand, the drywall wrap does not require the services of an additional trade and can be installed at the same time as the GWB is installed over the vertical wall surfaces and therefore the drywall wrap is generally less expensive than wood wrap.